Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects, for example, as discussed in detail in U.S. Pat. Nos. 6,016,038; 6,211,626, and 7,014,336 incorporated herein by reference.
For certain lighting applications, including security and comfort, light output can be adjusted based on the time of day. For home security, as an example, this is done to make it appear as if someone is home. For comfort, controlling light activation according to the time of day is often implemented to permit lights to go on automatically at a predetermined time, such as the morning when one would wake up. Alternatively, light might be regulated based on the time of day for home automation. In other cases, timing is needed in a light source to permit the light to change according to the time of day. However, such conventional solutions for time-based control of artificial light, do not take into consideration the color temperature change of natural light, or the intensity changes. A human's internal body clock, however, is originally driven by such changes in the light attributes.
Further, instant changes in light intensity are generally not appealing to the human eye, while more gentle changes are more comfortable. Accordingly, it is desirable to have a light source that will gently fade-in the intensity of emitted light from a low or zero intensity to the chosen final intensity during darker times of day or in a dark space. It is similarly desirable to have a light source that will gently fade-out the intensity of emitted light from the initial, bright intensity to a low or zero intensity during darker times of day or in a dark space. It is also desirable to have a light source that ramps up or down quickly during brighter times of day or in a bright space, as less acclimation is required by the user's eye.
While lighting units or light sources exist that gently ramp up or down the intensity of light, these systems do not account for the time of day or year, or the geophysical location of the light source. Thus, there is a need in the art for a lighting unit or light source that can adjust the lighting profile based on the time of day or year, that can optionally consider the geophysical location of the light source, and that can calibrate an internal clock mechanism utilizing data from an ambient light level sensor.